Use gpu::Mailbox instead of std:string in IPCs

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 84ed365803cb7a9b46ee53045325e7df067a238a..21c582e30da5fb5ab52ff6b1c3b84ccf52c894c2 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -40,6 +40,10 @@ class Rect;
 class Size;
 }
 
+namespace gpu {
+struct Mailbox;
+}
+
 namespace ui {
 
 class Compositor;
@@ -112,12 +116,12 @@ class COMPOSITOR_EXPORT Texture : public base::RefCounted<Texture> {
   virtual unsigned int PrepareTexture() = 0;
 
   // Replaces the texture with the texture from the specified mailbox.
-  virtual void Consume(const std::string& mailbox_name,
+  virtual void Consume(const gpu::Mailbox& mailbox,
                        const gfx::Size& new_size) {}
 
   // Moves the texture into the mailbox and returns the mailbox name.
   // The texture must have been previously consumed from a mailbox.
-  virtual std::string Produce();
+  virtual gpu::Mailbox Produce();
 
  protected:
   virtual ~Texture();